AD/AL 250/89 - Gas Producer Rotor Tie Bolt

The directive operates around a small set of core technical and regulatory concepts: applicability (engine models and part numbers), a mandatory removal and non‑installation requirement, a compliance timetable, cross‑reference to manufacturer technical material, and the regulator’s stated safety rationale.

Applicability: The AD identifies the class of engines in scope by model, listing RRC (formerly Allison) 250‑B17 series and 250‑C series engines: specifically 250‑B17, ‑B17B, ‑B17C, ‑B17D, ‑B17E, ‑B17F, ‑B17F/1, ‑B17F/2, 250‑C18, ‑C20, ‑C20B, ‑C20F, ‑C20J, ‑C20R, ‑C20R/1, ‑C20R/2, ‑C20R/4, ‑C20S and C20W (Applicability). This establishes the engine population to be addressed. The AD also maps the affected tie bolt part numbers in Table 1 and lists common aircraft installations in Table 2, while noting the list of aircraft is not exclusive (Applicability, Note 1; Table 2).

Hard prohibition on installation: From the AD's effective date operators may not install any of the Table 1 P/Ns in any RRC 250‑B or 250‑C engines (Requirement, para 2). This creates an immediate restriction on future maintenance choices for operators, maintenance organisations and parts suppliers.

Removal/replace requirement with a flexible timing window: Replacement of listed tie bolts is required either at the next disassembly of the engine for any reason or by 31 October 2011, whichever occurs first (Compliance para 1). This creates a staging of compliance that prioritises safety at disassembly events and imposes an absolute deadline for replacement. The AD therefore allows continued operation until disassembly, subject to the prohibition on installing new listed P/Ns.

Cross‑reference to manufacturer and FAA materials: The AD refers to RRC Commercial Engine Bulletins (CEBs) CEB A‑304, CEB A‑1371, CEB A‑72‑4076, TP CEB A‑176, TP CEB A‑1319, TP CEB A‑72‑2027 (Revision N/C, dated 23 May 2005) and EXTEX Service Bulletin T‑090, Revision N/C, dated 23 May 2005, as materials that "pertain to the subject" (Related Information). It also refers to FAA AD 2006‑13‑06 (Note 2). These references supply the technical background and instructions that operators will need to select compliant replacement tie bolts and the maintenance procedures to effect replacement. The AD itself does not specify torque values, installation procedures, or approved alternative P/Ns; it points to the manufacturers' technical documents for that information.

Safety trigger and intended outcome: The stated trigger for the AD is eleven reported tie bolt failures attributed to high‑cycle fatigue and the hazard is described as potential loss of engine power, first stage turbine wheel overspeed and an uncontained engine failure (Background). The intended outcome is to prevent tie bolt failure by removing the specific P/Ns that have failed in service and stopping their further installation.

Regulatory mechanics: The AD text is compact and prescriptive: it defines the affected components, prescribes actions (remove and replace; do not install), and sets specific deadlines. It does not include explicit enforcement penalties or administrative procedures within the text; the directive "becomes effective on 31 August 2006" and is signed by a CASA delegate (James Coyne) (Effective date; signature block). The AD therefore functions as a mandatory technical requirement whose substantive content is technical and part‑specific, while enforcement and administrative follow‑up are governed by the regulatory framework under which CASA issues ADs , the AD itself contains the operative technical instructions and the references necessary for implementing them.

The AD affects a defined set of actors through its combination of applicability clauses, part‑number lists and aircraft examples. Primary affected parties are engine operators, aircraft operators, maintenance organisations, parts suppliers, and manufacturers who service or supply Allison/RRC 250‑B and 250‑C series engines or the listed tie bolt P/Ns.

Engine and aircraft operators: Any operator of aircraft fitted with the listed RRC 250‑B and 250‑C series engines that have installed tie bolts with P/Ns listed in Table 1 is directly affected (Applicability). Table 2 lists a non‑exhaustive set of aircraft that commonly carry these engines , examples include Agusta A109 variants, Bell 206A/B/L, Eurocopter AS355 variants, Eurocopter BO‑105 variants, McDonnell Douglas 369 series and others , but the AD explicitly states the engine/part applicability is not limited to the aircraft listed. As such, operators of any aircraft with these engines must check the tie bolt P/Ns against Table 1.

Maintenance organisations and licensed engineers: The AD prescribes component removal and replacement at disassembly or by a deadline. Licensed maintenance organisations and certifying staff performing engine disassembly, overhaul or replacement will be responsible for identifying the P/Ns, ordering replacement parts with non‑listed P/Ns, and performing the replacement in conformance with manufacturer guidance (Requirement; Related Information). They will also be responsible for complying with the prohibition on installing listed P/Ns from the AD's effective date.

Parts suppliers and distributors: The AD directly affects suppliers that manufacture or distribute the listed P/Ns. Table 1 identifies several manufacturers and specific P/Ns: EXTEX Ltd. (A23008020, E23008020), Rolls‑Royce Corporation (23008020, 6843388, 6876991), Superior Air Parts Inc. (A23008020) and Pacific Sky Supply Inc (23008020P) (Applicability, Table 1). Suppliers dealing in those numbers must ensure they do not provide or install the listed P/Ns in the engines covered by the AD, at least from the effective date.

Engine and airframe manufacturers, and technical publishers: The AD references RRC Commercial Engine Bulletins and EXTEX Service Bulletin as the supporting technical documents (Related Information). Manufacturers and technical publishers who issue or rely on those documents will be part of the information flow operators use to implement the AD. Rolls‑Royce and EXTEX are explicitly named.

Regulator and delegate: The AD is issued by CASA and signed by a delegate, James Coyne (signature block); CASA, via its enforcement and certification arms, is the issuing authority. The AD's effective date is 31 August 2006 (Effective date).

Indirectly affected parties: Insurers, lessees and financiers have an interest because an AD that requires component removal and replacement creates immediate maintenance obligations that affect airworthiness status, downtime and cost. The AD does not mention insurance or leasing, but operators and financiers will need to track compliance to preserve airworthiness certificates and contractual obligations.

Geographic scope and cross‑jurisdictional effect: The AD references FAA AD 2006‑13‑06 (Note 2). That indicates the same or similar safety issue has been addressed by the United States regulator and suggests cross‑jurisdictional coordination or at least parallel action. Operators who operate internationally or who source parts cross‑border must account for the AD's requirements in multiple regulatory frameworks.

What each actor must do and who pays: Practically, the on‑aircraft operator pays for replacement parts and labour when the engine is next disassembled or by the absolute deadline. Maintenance organisations supply labour and technical competence to perform the replacements. Parts suppliers may incur inventory or scrappage costs if they hold the listed P/Ns that the AD prohibits installing. Manufacturers may supply replacement parts not listed in Table 1 and will be consulted via the referenced CEBs and service bulletin. The AD text itself prescribes who must act (anyone operating the affected engines) but does not specify cost allocation mechanisms; those are handled by contractual relationships among owners, operators, maintenance providers and suppliers.

The AD sets out a narrow set of prescriptive duties for operators and maintenance personnel, while the document itself does not enumerate rights, remedies, or administrative appeal mechanisms. The operative duties and their practical content are as follows.

Duty to identify affected parts and engines: Operators and maintenance organisations must identify whether any engine within their control is an RRC 250‑B or 250‑C series engine and whether that engine contains tie bolts with the P/Ns listed in Table 1 (Applicability; Table 1). The AD presents the affected P/Ns explicitly: EXTEX A23008020 and E23008020; RRC 23008020, 6843388 and 6876991; Superior A23008020; Pacific Sky Supply 23008020P. Identification is an express precondition for the replacement duty.

Duty to remove and replace listed tie bolts: Paragraph 1 of the Requirement instructs: "Remove from service the P/N gas producer rotor assembly tie bolts listed in Table 1 of this Airworthiness Directive, and replace with tie bolts with P/Ns that are not listed in Table 1 of this Airworthiness Directive." This duty is a strict obligation to remove the specified components and to replace them with alternatives whose P/Ns are not those listed in Table 1.

Duty not to install listed tie bolts: Paragraph 2 of the Requirement creates an immediate and absolute prohibition: "Do not install any gas producer rotor assembly tie bolt P/Ns listed in Table 1 of this AD in any RRC 250‑B and 250‑C Series turboprop and turboshaft engines." That duty applies from the AD's effective date (see Compliance para 2). The wording leaves no room for selective installation of listed P/Ns after the effective date.

Timing duty with a two‑part trigger: Compliance paragraph 1 sets the timing boundary: replacement must take effect "At the next time they are disassembled for any reason, or by October 31, 2011, whichever occurs first." The duty is therefore event‑driven (disassembly) or time‑bound (absolute deadline). For engines that are not disassembled before the deadline, the operator must ensure replacement by the deadline.

Reference duty to manufacturer guidance: The AD signals that operators should consult the listed RRC Commercial Engine Bulletins and EXTEX Service Bulletin because these documents "pertain to the subject of this Airworthiness Directive" (Related Information). While the AD does not explicitly require following those documents, they are referenced as relevant technical guidance, and the replacement imperative implicitly requires following appropriate technical procedures for replacement, which the manufacturer's bulletins supply.

Rights and omissions in the AD text: The AD text does not set out procedural rights to seek exemptions, nor does it include administrative review processes or penalty schedules. It does not specify which alternative P/Ns are approved; it requires replacement with P/Ns not listed in Table 1, leaving the identification of acceptable alternatives to the operator in consultation with manufacturers and the referenced technical materials. The AD also does not specify whether replacement parts require specific certification, but the reference to manufacturer CEBs implies that technical conformity and installation instructions are contained there.

Practical consequences of duties: The combination of duties creates immediate and ongoing maintenance controls: operators must (1) log and trace the P/Ns of installed tie bolts, (2) refrain from installing the listed P/Ns after the effective date, (3) schedule replacements at the next disassembly or by the absolute deadline, and (4) use the manufacturer CEBs and service bulletin for technical details. These duties allocate the operational burden to owners and maintainers; the AD prescribes the technical outcome but delegates selection of replacement P/Ns and the detailed installation steps to manufacturer guidance and the operator's maintenance procedures.

Delegation and decision makers: The AD is signed by a CASA delegate, establishing that CASA has issued the technical requirement; the decision to replace, timing within the AD's parameters and selection of replacement P/Ns rests with operators and their maintenance organisations, in line with the AD's technical references. The AD does not name an approval body for alternative P/Ns within the text; that function would ordinarily be performed through the manufacturer's technical documentation and the existing airworthiness certification framework, though those mechanisms are not described in the AD itself.

The text of this Airworthiness Directive is concise and prescriptive on technical obligations but does not itself set out enforcement mechanisms, monetary penalties or criminal sanctions. The AD states the effective date, prescribes removals and non‑installation, references manufacturer documents, and is signed by a CASA delegate, but it does not include an enforcement or penalty clause within the document.

What the AD does state: The directive "becomes effective on 31 August 2006" and is issued by CASA (Effective date; signature block). It prescribes mandatory removal and installation restrictions and sets compliance timings (Requirement; Compliance). Those are the operative commands of the AD.

What the AD does not state: The document does not contain explicit language on penalties for non‑compliance, does not specify administrative procedures for enforcement (such as notices, suspension of certificates, fines, or grounded aircraft), and does not provide an appeal or exemption process within the text. It neither quantifies regulatory sanctions nor lists inspection or reporting procedures following compliance. Consequently, the AD itself leaves enforcement detail outside its text.

Implications and likely enforcement channels (grounded in the AD's nature): Because this instrument is an Airworthiness Directive , a regulatory tool used to address known safety defects , compliance is presented as mandatory within the scope of its applicability. The AD references manufacturer technical materials and provides specific technical requisites. In practice, enforcement of an AD occurs through the regulator’s broader airworthiness and safety oversight powers and through the airworthiness certification system (for example, continued fitness for flight is contingent on compliance with applicable ADs). The AD does not describe those mechanisms, so the document should be read as issuing technical obligations that will be enforced within CASA’s regulatory framework rather than as a self‑contained enforcement schedule.

Operational consequences of non‑compliance (documented hazard): The Background describes a concrete safety risk , eleven reported tie bolt failures due to high‑cycle fatigue that could cause loss of engine power, first stage turbine wheel overspeed and an uncontained engine failure. The operational consequence of not complying therefore includes exposure to that hazard. While the AD does not state statutory penalties, operating an aircraft in contravention of an AD that addresses a safety‑critical failure is likely to have regulatory and commercial consequences (for example, increased scrutiny by the regulator, potential grounding, or insurer and contractual issues). Those consequences are inferential from the AD's safety rationale and mandatory commands but are not enumerated in the text.

Cross‑jurisdictional enforcement note: The AD references FAA AD 2006‑13‑06 (Note 2). That reference suggests the FAA has taken corresponding action. For internationally operated aircraft and components, compliance is relevant to regulators beyond CASA; the AD itself does not coordinate enforcement measures with other states, but operators should expect that international airworthiness regimes will treat AD compliance as material to airworthiness status.

Record‑keeping and audit expectation: The AD requires technical action but does not prescribe specific record‑keeping language. In practice, demonstrating compliance for audit or inspection will require records showing identification of affected P/Ns, replacement work orders, parts invoices for replacement parts with P/Ns not listed in Table 1, and any application of manufacturer bulletins cited in the AD. The AD does not itself mandate the records to produce on demand, but compliance evidence is ordinarily part of regulatory oversight.

In short, the AD imposes technical obligations; it does not include enforcement mechanisms or penalties in its text. Enforcement and any penalties will be exercised under CASA’s broader regulatory powers and associated rules outside the body of this AD; the AD itself presents the mandatory technical requirements and the safety rationale.

The AD is a discrete technical regulatory instrument that sits within the broader aviation safety framework and interacts, by reference, with manufacturer technical documentation and at least one foreign regulator action. The text explicitly cross‑references other instruments and, by its nature, implies interaction with airworthiness certification rules and maintenance standards though it does not quote or reproduce those laws.

Reference to manufacturer bulletins and service bulletins: The AD lists a series of Rolls‑Royce Corporation Commercial Engine Bulletins (CEBs) , CEB A‑304, CEB A‑1371, CEB A‑72‑4076, TP CEB A‑176, TP CEB A‑1319, TP CEB A‑72‑2027 (Revision N/C, dated 23 May 2005) , and EXTEX Service Bulletin T‑090, Revision N/C, dated 23 May 2005, as "pertain[ing] to the subject of this Airworthiness Directive" (Related Information). Those documents typically contain the technical procedures, tolerances, torque values and approved parts lists that are necessary to perform safe replacements. The AD uses those documents as technical adjuncts: the AD prescribes the mandatory action (remove and replace), while the manufacturer material provides the means to do so. This establishes a practical regulatory interaction between CASA’s directive and manufacturer technical law‑like materials.

Reference to foreign regulator action: Note 2 explicitly states "FAA AD 2006‑13‑06 Amdt 39‑14659 dated 14 June 2006 refers." That indicates coordination or parallel action between CASA and the United States Federal Aviation Administration. For operators and maintenance organisations operating across jurisdictions, compliance with both CASA and FAA ADs will be relevant. The AD does not state whether CASA’s directive is identical or diverges from the FAA AD; it simply notes the FAA action as related information.

Interplay with airworthiness certification and maintenance rules (implied): The AD imposes component‑level requirements that will affect the airworthiness status of affected engines and aircraft. Although the AD does not cite the specific statutory provisions of the Civil Aviation Act or the Civil Aviation Safety Regulations, an AD typically functions in the operational space governed by those instruments; the AD’s requirements therefore operate in practice alongside requirements for maintenance, continuing airworthiness, and certification. The AD itself is not a statute but a regulatory instrument issuing a technical mandate that complements statutory airworthiness obligations. The text does not state the precise legal mechanism linking AD compliance to airworthiness certification; readers should treat the AD as a mandatory technical instruction that interacts with the existing airworthiness regulatory framework.

Interaction with supply and parts law: The AD forbids installation of certain P/Ns from its effective date. That interacts with procurement and inventory law in the sense that suppliers and maintainers must track which P/Ns they hold and must not install prohibited parts. The AD references specific manufacturers and P/Ns, so supply‑chain records will be necessary to demonstrate compliance. The AD itself does not provide transition rules for existing inventory beyond the removal timetable.

Contractual and commercial interactions: The AD’s replacement obligation will affect maintenance contracts, leasing agreements and insurance relationships because it alters maintenance obligations and creates replacement expense and downtime. The AD does not legislate contractual arrangements; it imposes technical obligations that parties must reflect in contractual dealings. The AD does not mention insurance or leases, but these commercial instruments will interact in practice with the technical obligations imposed by the AD.

No specific exemptions or conflict resolution in the AD: The AD does not contain language about exemptions, tolerances or conflict resolution with other regulatory provisions. It therefore should be read as providing clear technical obligations that must be accommodated within the operator’s existing regulatory compliance framework.

In summary, the AD instructs operators to follow specific technical steps and points them to manufacturer and FAA materials. It interacts operationally with broader airworthiness law, maintenance requirements, supply‑chain obligations and cross‑jurisdictional ADs, though the AD itself contains only the technical prescription and cross‑references rather than detailed legal integration language.

The document supplied contains the Airworthiness Directive as issued in 2006 and provides a few internal revision notations for referenced manufacturer documents, but it does not record subsequent amendments to the AD itself. The AD’s own metadata and internal references give the following temporal data points.

Issuance and effective date: The AD is designated AD/AL 250/89 9/2006 and is dated 9/2006 in the header. The signature block shows it was signed by James Coyne, Delegate of the Civil Aviation Safety Authority, on 21 July 2006, and the AD "becomes effective on 31 August 2006" (signature; Effective date). Those are the issuance and commencement markers contained in the document.

Referenced document revisions: The Related Information section lists RRC Commercial Engine Bulletins and an EXTEX Service Bulletin, each annotated "Revision N/C, dated 23 May 2005" for the RRC bulletins and "Revision N/C, 23 dated May 2005" for EXTEX Service Bulletin T‑090 (Related Information). Those revision notations indicate the state of the manufacturer technical documents at the time the AD was issued; they are not amendments to the AD, but they contextualise the technical guidance applicable at the time.

Note of related FAA action: The AD notes FAA AD 2006‑13‑06 Amdt 39‑14659 dated 14 June 2006 as referencing the same issue (Note 2). The presence of the FAA AD date indicates a near contemporaneous action by the FAA, which may have influenced CASA’s issuance schedule. The AD does not record amendments to itself resulting from the FAA action.

Absence of recorded amendments in the text: The document does not include an "Amendment" or "History" section listing subsequent changes to the AD text, no later effective dates are shown, and there is no text indicating that the AD has been superseded or revised. Therefore, within this document's contents there is no amendment history beyond its initial issuance.

What is not in the document: The AD does not provide a history of prior AD numbers for the same hazard, it does not indicate any prior versions of AD/AL 250/89, and it does not include a sunset clause or scheduled review date. It also does not include a record of corrections, reissues, or amendments. If later amendments exist, they are not captured in the supplied text.

Practical consequence for users seeking amendment information: Users relying on this AD should treat the document as the 2006 issuance and consult CASA’s official database or regulatory repository for any subsequent amendments, superseding ADs or revocations. The AD itself gives the effective date and the signature of the delegate, but it does not provide a record of further legislative or regulatory changes. The manufacturer bulletins referenced have their own revision dates noted (23 May 2005), but the AD does not incorporate any later revisions of those documents.

In short, the AD as supplied contains its original issuance details and the contemporaneous references to manufacturer and FAA materials, but it does not contain a later amendment history within the text supplied.

The supplied Airworthiness Directive does not include or reference any litigation history, court decisions, or tribunal outcomes. The text is limited to the technical prescribing language, references to manufacturer bulletins and the FAA AD, and administrative metadata (signature, effective date). There are no citations to judicial or administrative decisions in the document.

What the AD records: The document records the regulator's action, the safety rationale (eleven reports of tie bolt failure due to high‑cycle fatigue), the prescriptive requirements, and related manufacturer and FAA documents. It does not claim any adjudicative or dispute history arising from the AD's issuance.

What the AD does not record: The AD does not state whether any operator or third party challenged the AD, whether CASA issued enforcement notices related to the AD, or whether any disputes arose in courts or administrative tribunals as a consequence. No litigation outcomes, case names, or procedural histories are supplied.

Implication for legal research: If a practitioner needs litigation background , for example, to see whether the AD was challenged on procedural or substantive grounds, or whether compliance disputes resulted in legal precedent , the AD itself provides no such material. The user will need to search judicial and administrative databases, and CASA records, external to the document. The AD’s cross‑reference to the FAA AD might provide another avenue to locate litigation or enforcement outcomes in the United States, but again the AD does not itself report litigation.

Therefore, in the absence of additional source material, the document should be treated as a technical regulatory instrument without recorded litigation history. Any assertion about subsequent legal proceedings would require consultation of other primary sources outside the AD.

The AD is brief but contains several practical hazards and potential traps for operators, maintainers and parts suppliers. These "gotchas" derive directly from the AD’s wording, timing structure and cross‑references.

1. Two distinct obligations with different timing The AD contains two separate obligations with different temporal effects. Paragraph 2 of the Requirement provides an immediate prohibition on installing any P/N listed in Table 1 "from the effective date of this Airworthiness Directive" (Requirement para 2; Compliance para 2). Paragraph 1 requires removal and replacement "At the next time they are disassembled for any reason, or by October 31, 2011, whichever occurs first" (Requirement para 1; Compliance para 1). Practically, this means an operator may lawfully continue to operate an engine that currently contains a listed P/N until the next disassembly or until the 2011 deadline, but must not re‑install the listed P/Ns if a component change or disassembly occurs after the AD’s effective date. This staggered approach can be a compliance trap: staff who assume all affected bolts must be replaced immediately will incur avoidable costs, while staff who overlook the prohibition on installation may inadvertently breach the AD by installing a listed P/N during maintenance.

2. "Not limited to" aircraft list Table 2 lists applicable aircraft models but the AD expressly states these engines are installed on, but not limited to, the aircraft listed (Applicability, Note 1). That language widens the scope beyond the table, so fleet managers cannot rely on the table alone to determine applicability. They must check their engines' model numbers and tie bolt P/Ns irrespective of aircraft model lists.

3. Specific P/Ns and overlapping manufacturer part numbers Table 1 lists identical or similar P/Ns across multiple manufacturers (for example A23008020 is shown under EXTEX and Superior Air Parts Inc.). Parts with similar P/Ns from multiple sources may be confused in inventory. Operators must verify manufacturer and full P/N records; substitution of a visually similar part or mislabelled stock could result in installing a prohibited P/N.

4. Replacement parts are defined negatively The AD mandates replacement "with tie bolts with P/Ns that are not listed in Table 1." The AD does not list approved alternative P/Ns or specify an approval pathway for replacement parts. That leaves open the question: what P/Ns are acceptable? Operators must consult the referenced RRC CEBs and EXTEX service bulletin (Related Information) and manufacturers for approved replacement parts. If the operator selects an alternative without manufacturer approval, they may create compliance uncertainty.

5. Reference documents dated prior to AD The RRC and EXTEX documents referenced for technical instructions are dated 23 May 2005 and are indicated as "Revision N/C" (Related Information). These references pre‑date the AD. Operators must ensure they consult the correct revision and confirm whether later revisions exist; the AD does not incorporate subsequent revisions, and following a later manufacturer revision may be appropriate but requires confirming its applicability.

6. Deadline provides long run‑in The absolute deadline of 31 October 2011 (over five years after the AD's effective date) may create operational incentives to defer replacement until scheduled disassembly, which conserves resources but leaves the aircraft operating with potentially failure‑prone components for years. That is a policy trade‑off set by the AD and can be a risk management decision for operators balancing safety risk, operational necessity and cost.

7. Lack of explicit enforcement language The AD does not state enforcement actions, penalties or required reporting. This absence can cause ambiguity about what evidence the regulator will expect to see in an audit. Operators should not interpret silence as absence of enforcement; they should prepare documentary evidence of compliance, including part numbers, maintenance records and use of the referenced bulletins.

8. Multiple stakeholders affected The AD names suppliers and manufacturers. If parts supply chains cross borders or involve differing P/N naming conventions, ensuring compliance across procurement channels can be complicated. For example, an operator might buy a "like‑numbered" part from a different supplier that is actually acceptable, or might receive a prohibited P/N by mistake. Inventory controls must be precise.

9. Record and procurement mismatch risk The AD requires replacement with non‑listed P/Ns but does not instruct how to document the replacement. In practice, operators must capture part‑number changes in maintenance logs, invoices, and traceability records. Failure to do so can make it hard to demonstrate compliance at audit or in the event of an incident.

10. Cross‑jurisdictional operations The AD references FAA AD 2006‑13‑06. Companies operating in multiple jurisdictions must ensure compliance with both CASA and any other relevant regulators’ directives; differences in timing or scope between ADs can create operational complexity, and the AD does not detail how to reconcile any differences.

These items are drawn directly from the AD’s wording and structure. They identify places where the AD’s brevity and technical focus create practical choices and compliance risks for operators, maintainers and suppliers.

Compliance proceeds through a series of concrete steps grounded in the AD's language and the manufacturer's referenced materials. The AD prescribes the objectives: identify affected tie bolt P/Ns, cease installing listed P/Ns from the effective date, and remove and replace listed bolts at the next disassembly or by 31 October 2011. The following is a practical step‑by‑step checklist an operator or maintenance organisation should follow, based on the AD.

1. Confirm AD applicability to your fleet

• Verify whether any aircraft in your fleet contain Rolls‑Royce Corporation (formerly Allison) 250‑B or 250‑C series engines as listed in the AD (Applicability). The AD lists specific engine model numbers; check engine data plates and records to confirm model numbers.

2. Inventory and identify tie bolt P/Ns

• Inspect maintenance records and perform a physical verification (if records uncertain) to identify the gas producer rotor assembly tie bolt part numbers installed in each engine. Compare each P/N to Table 1 in the AD. Table 1 lists: EXTEX A23008020 and E23008020; RRC 23008020, 6843388 and 6876991; Superior A23008020; Pacific Sky Supply 23008020P (Applicability, Table 1).
• Where the same P/N exists under multiple manufacturer names, verify manufacturer origin and batch numbers to ensure correct identification.

3. Implement immediate non‑installation control

• From the AD's effective date (31 August 2006), instruct maintenance teams and procurement not to install any P/Ns listed in Table 1 on any RRC 250‑B or 250‑C series engines (Requirement para 2; Compliance para 2).
• Update procurement approvals, parts ordering systems and stores to bar these P/Ns for installable stock and to flag any incoming stock with those P/Ns.

4. Plan removal and replacement work

• For engines that contain a listed P/N, schedule removal and replacement at the next disassembly event for any reason. If an engine will not be disassembled before 31 October 2011, schedule replacement before that deadline (Requirement para 1; Compliance para 1).
• Coordinate with maintenance organisations and line maintenance to ensure the work is done at the next feasible disassembly, including during scheduled overhauls, hot section inspections or other disassembly events.

5. Identify acceptable replacement parts and procedures

• Consult the referenced RRC Commercial Engine Bulletins (CEBs) and EXTEX Service Bulletin T‑090 for the technical procedures and for guidance on acceptable replacement part numbers and installation procedures (Related Information). The AD names the CEBs: CEB A‑304, CEB A‑1371, CEB A‑72‑4076, TP CEB A‑176, TP CEB A‑1319, TP CEB A‑72‑2027 (Revision N/C, 23 May 2005), and EXTEX Service Bulletin T‑090 (Revision N/C, 23 May 2005).
• If clarification is required regarding what replacement P/Ns are acceptable or whether using a particular non‑listed P/N requires further approval, contact Rolls‑Royce (RRC) or the part manufacturer for written confirmation and technical guidance.

6. Execute work in accordance with manufacturer guidance

• Perform removal and installation using the procedures and torque/settings specified in the manufacturer documents referenced by the AD. Record all work in the aircraft/engine maintenance log, including the old and new part numbers, serial numbers, batch numbers, and any relevant CEB or service bulletin references used for the task.

7. Document compliance

• Maintain a compliance file that includes: date of AD issue and effective date; engines inspected and a list of those with Table 1 P/Ns; details of replacement parts used (P/Ns not listed in Table 1); work orders and sign‑offs by certifying maintenance staff; invoices or procurement records for replacement parts; and references to any CEBs or service bulletins followed.
• For engines retained with listed P/Ns pending disassembly, maintain a schedule showing the planned disassembly or the deadline (31 October 2011) to demonstrate active management of compliance obligations.

8. Control spare parts and vendor relations

• Notify parts suppliers and vendors about the AD and the prohibition on installing listed P/Ns. Request written assurances from suppliers that parts shipped for installation are not P/Ns listed in Table 1.
• Quarantine inventory of listed P/Ns to prevent accidental installation and to decide on disposition in accordance with the supplier, manufacturer or regulator guidance.

9. Monitor related regulatory and manufacturer updates

• Track Rolls‑Royce and EXTEX for any additional service bulletins, clarifications, or updated CEBs. Monitor CASA’s AD database for any amendments or follow‑ups and be aware of FAA AD 2006‑13‑06 for cross‑jurisdictional consistency (Note 2).
• If operating internationally, verify whether foreign regulators have additional or different requirements for equivalent engines and parts.

10. Prepare for audits and inspections

• Ensure the maintenance records, part traceability and the compliance file are audit‑ready. While the AD does not list explicit enforcement procedures, operators should be prepared to demonstrate compliance in oversight audits or incident investigations, and show that the actions were taken in accordance with the AD and the referenced technical documents.

11. Consider commercial and operational planning

• Factor maintenance downtime and the cost of replacement parts into scheduling and budgeting. Communicate with insurers, lessors and other stakeholders about the plan to comply and expected timelines for replacement if appropriate under contractual obligations.

12. Seek clarification where required

• If any ambiguity exists concerning acceptable replacement P/Ns, the timing or interpretation of "next disassembly," obtain written technical guidance from the manufacturer or an authorised representative and, if necessary, seek clarification from CASA through the appropriate regulatory channel.

These steps follow the AD’s prescriptive language , identify affected P/Ns, cease installing them after the effective date, replace them at disassembly or by the specified deadline, and use referenced manufacturer materials for technical implementation. The AD does not itself provide approved replacement part numbers or detailed installation data, so successful compliance requires following the RRC CEBs and EXTEX Service Bulletin referenced in the AD and maintaining documentary evidence of the work performed.